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The study in the UK is not the only investigation into the role of sunshine in maintaining cardiovascular health. Other research has found:
- High cholesterol cancels out some of the benefits of sunshine. A study in Spain found that people who had untreated high cholesterol tended to have lower levels of vitamin D, even if they got lots of sun, even during the summer. People who took statins - cholesterol lowering drugs to control high cholesterol had higher levels of vitamin D.
- Smoking cancels out some of the benefits of sunshine, even in sunny climates, and even in summer.
- Vitamin D status affects both bone and muscle strength, and helps prevent injuries that would interfere with getting enough exercise to support cardiovascular health.
- In the People's Republic of China, nearly everyone of any age fails to get enough sun, and nearly everyone needs to take a vitamin D. One of the seldom-reported findings of the famous China Study was that the best predictor of whether people in China would develop cardiovascular disease was whether or not they received enough sunshine, more than diet, antioxidant, or vitamin status.
- In the United States, however, it may be possible to get too much sunshine for cardiovascular health. A study by the Nutritional Epidemiology Branch of the National Cancer Institute of 346,615 fair skinned Americans found that those who got the most sunshine were slightly more likely, about 6% more likely, to develop cardiovascular disease, and the trend was significant (that is, the data did not suggest that there was any possibility that getting the highest levels of sun exposure might actually reduce the risk of cardiovascular disease).
- Vitamin D deficiency only seems to be a marker of cardiovascular disease, not a cause of cardiovascular disease. Having low vitamin D levels suggests that there is a higher risk of developing heart disease, but taking a vitamin D supplement will not necessarily lower the risk of developing heart disease.
That is because not getting enough sunshine both reduces the production of vitamin D and reduces the conversion of nitrates into nitric oxide by the skin. Getting enough sunshine will both restore production of vitamin D, which has many other uses in the body, and increase the production of nitric oxide to dilate blood vessels.
It is critical that the sun's UV rays not be blocked by sunscreen or sun block during those 20 minutes, however, or they will not convert nitrates into the nitrites needed to lower blood pressure, and they cannot used by the sun to power the production of vitamin D.